Fuel sulfur content-based operation control of a diesel engine

ABSTRACT

Over a diesel engine&#39;s lifetime, engine efficiency may be reduced and some of this may be attributable to sulfur deposit accumulation in the engine. A method for controlling operation of a diesel engine operating on a fuel is provided. The method may include adjusting an injection of fuel to the engine in response to a sulfur content of the fuel.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application61/101,533, filed on Sep. 30, 2008, entitled FUEL SULFUR CONTENT-BASEDOPERATION CONTROL OF A DIESEL ENGINE, the entirety of which is herebyincorporated herein by reference for all purposes.

FIELD

The present application relates to a method for controlling operation ofa diesel engine operating on a sulfur-containing fuel.

BACKGROUND AND SUMMARY

Diesel engines are typically used for on- and off-roadway vehicles, aswell as marine, industrial, and military use. While most of theindustrialized world's diesel fuel usage for on-highway applications isbeing reduced in sulfur content, high sulfur content fuel is still usedin some markets and applications. Sulfur in diesel fuels can have manydetrimental affects on modern high performance diesel engines, includingaccelerated wear, corrosion of internal components, and is particularlydamaging to emission control equipment.

Further, the inventors have discovered sulfur-contaminated fuel cancause fuel injector fouling, at least in part by sulfur deposits.Injector fouling can affect fuel injection quantity and the spraypattern of fuel injectors, thereby leading to degraded engine power, andvarious other effects.

At least some of the above issues of fuel injector fouling are addressedby a method for controlling operation of a diesel engine operating on asulfur containing fuel. The method may include adjusting an injection offuel to the engine in response to a sulfur content of the fuel tocompensate for degradation of fuel injectors.

For example, by adjusting fuel injection parameters based on sulfurcontent of the fuel, engine power can be maintained by compensating forthe potential clogging of the injectors due to sulfur deposits.

In another example, some issues may be addressed by a method formonitoring operation of a diesel engine operating on such a fuel, themethod comprising indicating fouling of a fuel injector in the engine inresponse to the sulfur content of the fuel. In this way, maintenance orother action may be taken to address high sulfur fuels.

In still another example, issues may be addressed by a method forcontrolling operation of a diesel engine operating on such fuel, themethod comprising performing a fuel injector cleaning cycle in responseto a sulfur content of the fuel. Again, by performing cleaning of thefuel injectors responsive to fuel sulfur content, degraded engineperformance may be addressed.

In yet another example, issues may be addressed by a method forcontrolling operation of a diesel engine operating on such fuel,comprising: estimating a sulfur content of the fuel based on fuelinjector performance; and adjusting operation based on the estimatedsulfur content of the fuel. In some examples, the adjusting operationmay include adjusting engine operation. In a further example, the methodmay include adjusting a sulfur decontamination cycle of an emissioncontrol device coupled to the engine, the cycle adjusted responsive tosulfur content of the fuel, the sulfur content correlated to injectorperformance of injectors coupled in the engine. In some examples, thefuel injector performance may include fuel injector effects on maximumengine power. In some examples, the fuel injector performance mayinclude an amount of fuel injected for a given pulsewidth at a given setof operating conditions. The operating conditions may include injectionpressure and/or engine speed. The amount of fuel injected may becalculated based on an exhaust air-fuel ratio and a mass airflow. Inthis way, improved performance may be achieved.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic diagram of a cylinder of multi-cylinder directinjection engine of a vehicle.

FIG. 2 shows example energy dispersive spectroscopy graphs showingsulfur deposit amount on fuel injector tips, based on a sulfur contentof the fuel used.

FIG. 3 shows an example graph showing reduction of engine power overtime at the same engine speed.

FIGS. 4-6 show example method flowcharts for operation control of adiesel engine based on sulfur content of the fuel.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example cylinder of a multi-cylinder engine of a vehiclethat may employ the present application. FIG. 2 shows example graphsillustrating greater sulfur deposit on fuel injector tips that weredispensing HS fuel compared to those dispensing ultra-low sulfur (ULS)fuels. Accordingly, FIG. 3 shows example changes in torque output overtime, for an engine using high sulfur (HS) fuel during an enginedurability test and an engine using ultra-low sulfur (ULS) fuel duringan engine durability test, thus illustrating that fuel injectors withgreater sulfur deposits may have greater reductions in engine power.FIGS. 4-6 show example method flowcharts for addressing, responding to,diagnosing, and/or reducing the accumulation of sulfur deposit on fuelinjectors to improve the maintenance of engine power and/or performanceover time.

FIG. 1 shows a schematic diagram showing one cylinder of multi-cylinderengine 10, which may be included in a propulsion system of an a vehicle.Engine 10 may operate on a fuel, such as diesel fuel, which may includevarying levels of sulfur. Engine 10 may perform compression ignition ofinjected fuel to thereby combust the fuel. Engine 10 may be controlledat least partially by a control system including controller 12 and byinput from a vehicle operator 132 via an input device 130. In thisexample, input device 130 includes an accelerator pedal and a pedalposition sensor 134 for generating a proportional pedal position signalPP. Combustion chamber (i.e. cylinder) 30 of engine 10 may includecombustion chamber walls 32 with piston 36 positioned therein. Piston 36may be coupled to crankshaft 40 so that reciprocating motion of thepiston is translated into rotational motion of the crankshaft.Crankshaft 40 may be coupled to at least one drive wheel of a vehiclevia an intermediate transmission system. Further, a starter motor may becoupled to crankshaft 40 via a flywheel to enable a starting operationof engine 10.

Combustion chamber 30 may receive intake air from intake manifold 44 viaintake passage 42 and may exhaust combustion gases via exhaust passage48. Intake manifold 44 and exhaust passage 48 can selectivelycommunicate with combustion chamber 30 via respective intake valve 52and exhaust valve 54. In some embodiments, combustion chamber 30 mayinclude two or more intake valves and/or two or more exhaust valves, orthe valve function may be accomplished via ports in the cylinder wallsthat are successively covered or uncovered by the piston.

In this example, intake valve 52 and exhaust valves 54 may be controlledby cam actuation via respective cam actuation systems 51 and 53. Camactuation systems 51 and 53 may each include one or more cams.

Fuel injector 66 is shown coupled directly to combustion chamber 30 forinjecting fuel directly therein in proportion to a signal received fromcontroller 12. In this manner, fuel injector 66 provides what is knownas direct injection of fuel into combustion chamber 30. The fuelinjector may be mounted in the side of the combustion chamber or in thetop of the combustion chamber, for example. Fuel may be delivered tofuel injector 66 by fuel tubes (AA) from an accumulator (or fuel rail)(BB), which receives fuel from a high pressure pump (CC).

The high pressure pump receives fuel from a fuel system (not shown)including a fuel tank, and a fuel pump. The high pressure pump variesthe pressure and quantity of fuel supplied to the rail and subsequentlyto the injectors in response to signals from the ECU. The components as10 described represent what is know as a High Pressure Common Rail fuelsystem, but the same functions can also be performed by other dieselfuel injection system designs such as pump-line nozzle, unit injector orhybrid systems, which employ different hardware components. The methodsof the invention could be applied to any of these fuel injection systemswith suitable adaptation.

Intake passage 42 may include a mass air flow sensor 120 and a manifoldair pressure sensor 122 for providing respective signals MAF and MAP tocontroller 12.

An emission control device, such as converter 70 can include multiplecatalyst bricks, in one example. In another example, multiple emissioncontrol devices, each with multiple bricks, can be used. Converter 70can be a NOx catalyst, SCR catalyst, oxidation catalyst, particularfilter, and/or combinations thereof.

Controller 12 is shown in FIG. 1 as a microcomputer including:microprocessor unit 102, input/output ports 104, read-only memory 106,random access memory 108, keep alive memory 110, and a conventional databus. Controller 12 is shown receiving various signals from sensorscoupled to engine 10, in addition to those signals previously discussed,including: engine coolant temperature (ECT) from temperature sensor 112coupled to cooling sleeve 114; a position sensor coupled to anaccelerator pedal; a measurement of engine manifold pressure (MAP) frompressure sensor 122 coupled to intake manifold 44; a measurement ofintake temperature (IT) or manifold temperature from a temperaturesensor; an engine position sensor from a Hall effect sensor 118 sensingcrankshaft 40 position; a measurement of exhaust temperature (ET) fromtemperature sensor 126; and a measurement of ambient temperature (AT)from external temperature sensor. In one aspect of the presentdescription, engine position sensor 118 produces a predetermined numberof equally spaced pulses every revolution of the crankshaft from whichengine speed (RPM) can be determined.

Storage medium read-only memory 106 can be programmed with computerreadable data representing instructions executable by processor 102 forperforming the methods described below as well as other variants thatare anticipated but not specifically listed.

As described above, FIG. 1 shows only one cylinder of a multi-cylinderengine, and that each cylinder may similarly include its own set ofintake/exhaust valves, fuel injector, etc.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The specific routines described herein may represent one or more of anynumber of processing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various acts,operations, or functions illustrated may be performed in the sequenceillustrated, in parallel, or in some cases omitted. Likewise, the orderof processing is not necessarily required to achieve the features andadvantages of the example embodiments described herein, but is providedfor ease of illustration and description. One or more of the illustratedacts or functions may be repeatedly performed depending on theparticular strategy being used. Further, the described acts maygraphically represent code to be programmed into the computer readablestorage medium in the engine control system.

As noted herein, the engine fuel, such as diesel fuel, may have varyinglevels of sulfur depending on the source of the fuel, etc. High sulfurlevels in the fuel may generate deposits on the fuel injectors (e.g.,injector 66). One approach to measure sulfur deposits on a fuel injectoris to perform energy dispersive spectrometry (EDS) on the fuel injector,wherein peaks at particular energy levels indicate the presence andrelative amount of an element. Specifically, when sulfur is present on asample, a peak will appear around 2.3 KeV. FIG. 2A illustrates anexample graph of energy dispersive spectrometry (EDS) of a fuel injectortip using HS fuel after an engine durability test. This graphillustrates a peak at an energy level of 2.3 KeV, as indicated by arrow125, indicating an amount of sulfur. FIG. 2B illustrates an examplegraph of EDS of a fuel injector tip using ULS fuel after the same test.The absence of a peak at 2.3 KeV in FIG. 2B, as indicated by arrow 127,indicates there may be greater sulfur deposits on the fuel injector tipusing HS fuel compared to the fuel injector tip using ULS fuel. Further,greater sulfur deposits may be observed on the fuel injector using HSfuel by scanning electron microscopy.

Accordingly, FIG. 3 shows torque output of an engine using HS fuel(solid line) and an engine using ULS fuel (dashed line) during an enginedurability test wherein engine speed was maintained throughout the test.As illustrated, the engine using HS fuel has a greater reduction intorque output compared to the engine using ULS fuel. This reduction maybe attributed, at least in part, to fuel injector fouling as wasdiscussed above with respect to FIG. 2. Note also that the examplegraphs here are shown as one particular correlation; however, the actualgraphs may vary due to engine configuration, engine design, operatingcycles, etc.

From FIGS. 2-3, it may be appreciated that the effect of sulfur on fuelinjector deposits (and thus performance, e.g., the amount of fuelinjected for a given pulsewidth (PW) at a given operating point,injection pressure, etc.) may be estimated based on the sulfur contentof the fuel, along with various operating parameters, such as the numberof hours the engine has operated, as just one example. In this way, itmay be possible to estimate the amount of sulfur deposits as well as thereduction in engine power on-line in the engine control system. As notedfurther herein, such estimations may be used for compensating fuelinjector sulfur deposits, such as to counteract such deposits, reducefurther increases in deposits, reduce deposits, etc. In one example,sulfur content of the fuel may be used to adjust timing for fuelinjector cleaning and/or catalyst regeneration.

A method for improving or maintaining torque output of an engine, basedon sulfur content of a fuel, is shown as a flowchart in FIG. 4. Engineoperating conditions (including engine speed, engine load, enginecoolant temperature, oxygen concentration in intake manifold 44, numberof hours of engine operation, etc.) may be determined at 410. The sulfurcontent of the fuel may be determined at 412. Sulfur content of the fuelmay be determined by correlating fuel injector performance to thebuild-up of sulfur deposits on the fuel injector. In one example, theamount of fuel injected for a given PW, at given operating conditions(engine speed, engine load injection pressure, temperature, etc.) may becorrelated to the sulfur content of the injected fuel. The amount offuel actually injected may be identified from exhaust air-fuel ratio andmass air-flow, as just one example, or by comparing the fuel flow fromthe high pressure pump with the expected or commanded flow through theinjectors. As the deposits build, less fuel may be injected for a givenPW due to restrictions caused by the sulfur deposits. Thus, as theamount of fuel injected decreases over the operation of the engine, anestimate of fuel sulfur content may be generated. As one example, if theamount of fuel injected for a given set of conditions decreases by 5%after 200 hours of engine operation, this may correlate to asufficiently high sulfur content to indicate that the sulfur content ofthe fuel is above a threshold value (e.g., an indication of HS fuel).For example, at 414, sulfur content of the fuel may be compared to apredetermined threshold. If sulfur content is higher than the threshold414, among other conditions, fuel injection pressure and/or fuel pulseduration (that is, the duration of fuel injector opening) may beincreased at 416 to counteract the reduction in engine power caused byfuel injector fouling. That is, as sulfur content of the fuel increases,the duration of fuel injector opening and fuel injection pressure mayincrease. Further, fuel injection timing may be adjusted at 416 tocounteract the engine power reduction.

It may be appreciated that adjustments in injection pressure, durationof fuel pulse, injection timing, and/or other operating parameters basedon sulfur content of the fuel, may be made by looking up predeterminedvalues in prestored tables. Alternately, the adjustment values may bedetermined by an algorithm accounting for various parameters includingengine operating conditions.

Referring now to FIG. 5, an example flowchart for indicating and/orperforming fuel injector cleaning, based on sulfur content of the fuel,is illustrated. The flowchart may illustrate a method for monitoringoperation of a diesel engine operating on a fuel. The method mayinclude, at 510, engine operating conditions may be determined. Further,sulfur content of the fuel may be determined at 512, similar to theexample in FIG. 4 described above. If sulfur content is above apredetermined threshold, at 514, and other operating conditions are met,an indication for early, and/or additional engine or injector cleaningmay be generated at 516. In one example, this indication may includesetting a diagnostic code in the controller 12. In another example, thisindication may include displaying a message in a vehicle message center,for example as a graphic icon on an interior display. In one example,the message may identify issues related to the sulfur content of thefuel. For example, the message may identify that the fuel sulfur contentis above a threshold limit. In another example, the message may requestmaintenance, or increased maintenance, related to fuel sulfur content(e.g., clean fuel injectors) or indicate said maintenance is beingperformed. Further, the indication may include an indication to performfuel injector cleaning and/or fuel injector replacement of one or morefuel injectors. It may be appreciated that the indicating may occurearlier as sulfur content of the fuel increases. Further, it may beappreciated that the indicating may be directed to the electronic driver68 or to the controller 12.

In another example, a fuel injector cleaning may be performed 518 byinitiating a fuel injector cleaning cycle. For example, a fuel injectorcleaning cycle may include increasing the temperature of combustion,thereby reducing or removing sulfur deposits. In one example, increasedcombustion temperature may be achieved by advancing injection timing.However, various other approaches may also be used, such as byincreasing engine load, adjusting valve timing, etc.

By the examples described with respect to FIG. 5, accumulation of sulfurdeposits on fuel injectors may be reduced.

A method for performing catalyst regeneration based on sulfur content ofthe fuel is shown as a flowchart in FIG. 6. In some cases the method mayillustrate a method for controlling operation of a diesel engineoperating on a fuel. Sulfur content of the fuel may be estimated basedon fuel injector performance 610. In this example, and in otherexamples, fuel injector performance may include an amount of fuelinjected for a given PW under a set of operating conditions, includinginjection pressure and engine speed, for example. Fuel injectorperformance may also be measured by changes in maximum engine output. At612, it may be determined if the sulfur content of the fuel is greaterthan a predetermined threshold. If the answer is yes, catalystregeneration may be performed 614 by, in one example, initiating sulfurdecontamination cycles (e.g., fuel injector cleaning cycles) of anemission control device (e.g. catalytic converter 70) coupled to theengine. The sulfur decontamination cycles may include increasing exhausttemperature to a high level sufficient to remove sulfur under reducing(e.g., rich) exhaust operating conditions. It may be appreciated thatthe initiation of the sulfur decontamination cycles may be initiatedearlier as sulfur content of the fuel increases or later as sulfurcontent of the fuel decreases. Further, timing of the sulfurdecontamination cycles may be otherwise modulated. By modulating thecatalyst regeneration based on sulfur content of the fuel, sulfurdeposit accumulation may be reduced and/or prevented.

It may be appreciated that the application disclosed herein may therebyaffect the quality and quantity of emissions and/or smoke from a dieselengine exhaust. Further, problems associated with clogged fuel injectorsmay be detected and/or fixed in a timely manner.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, two- or four-stroke, and other engine types.The subject matter of the present disclosure includes all novel andnonobvious combinations and subcombinations of the various systems andconfigurations, and other features, functions, and/or propertiesdisclosed herein.

The following claims particularly point out certain combinations andsubcombinations regarded as novel and nonobvious. These claims may referto “an” element or “a first” element or the equivalent thereof. Suchclaims should be understood to include incorporation of one or more suchelements, neither requiring nor excluding two or more such elements.Other combinations and subcombinations of the disclosed features,functions, elements, and/or properties may be claimed through amendmentof the present claims or through presentation of new claims in this or arelated application. Such claims, whether broader, narrower, equal, ordifferent in scope to the original claims, also are regarded as includedwithin the subject matter of the present disclosure.

1. A method for controlling operation of a diesel engine operating on afuel, comprising: adjusting a fuel injection timing to the engine inresponse to a sulfur content of the fuel.
 2. A method for controllingoperation of a diesel engine operating on a fuel, comprising: adjustinga fuel injection to the engine in response to a sulfur content of thefuel, wherein the adjusting includes adjusting a duration of fuelinjector opening and/or adjusting an injection pressure wherein theduration of fuel injector opening increases as the sulfur content of thefuel increases and/or the injection pressure increases as the sulfurcontent of the fuel increases.
 3. A method for monitoring operation of adiesel engine operating on a fuel, comprising: indicating fouling of afuel injector in the engine responsive to a sulfur content of the fuel,wherein the indicating includes setting a diagnostic code in acontroller.
 4. A method for monitoring operation of a diesel engineoperating on a fuel, comprising: indicating fouling of a fuel injectorin the engine responsive to a sulfur content of the fuel, wherein theindicating includes generating a message in a vehicle message center,the message identifying issues related to the sulfur content of thefuel, or identifying that the sulfur content of the fuel is above athreshold limit, or requesting maintenance or increased maintenancerelated to an increase in the sulfur content of the fuel.
 5. A methodfor monitoring operation of a diesel engine operating on a fuel,comprising: indicating fouling of a fuel injector in the engineresponsive to a sulfur content of the fuel, wherein the indicatingincludes an indication to perform fuel injector cleaning and/or fuelinjector replacement.
 6. A method for monitoring operation of a dieselengine operating on a fuel, comprising: indicating fouling of a fuelinjector in the engine responsive to a sulfur content of the fuel,wherein the indicating is further responsive to operating conditions ofthe diesel engine.
 7. A method for monitoring operation of a dieselengine operating on a fuel, comprising: indicating fouling of a fuelinjector in the engine responsive to a sulfur content of the fuel,wherein indications are generated earlier as the sulfur content of thefuel increases.
 8. A method for controlling operation of a diesel engineoperating on a fuel, comprising: performing a fuel injector cleaningcycle in response to a sulfur content of the fuel, wherein the fuelinjector cleaning cycle includes increasing combustion temperature, and,wherein the increasing combustion temperature is achieved by advancingfuel injection timing.
 9. A method for controlling operation of a dieselengine operating on a fuel, comprising: performing a fuel injectorcleaning cycle in response to a sulfur content of the fuel, whereinperforming includes performing the cycle earlier as the sulfur contentof the fuel increases and performing the cycle later as the sulfurcontent of the fuel decreases.
 10. The method of claim 9, wherein thefuel injector cleaning cycle includes increasing combustion temperature.11. A method for controlling operation of a diesel engine operating on afuel, comprising: estimating a sulfur content of the fuel based on fuelinjector performance; and adjusting operation based on the estimatedsulfur content of the fuel, wherein the fuel injector performanceincludes an amount of fuel injected for a given pulsewidth at a givenset of operating conditions, wherein operating conditions includeinjection pressure and engine speed.
 12. The method of claim 11, whereinthe adjusting operation includes adjusting engine operation.
 13. Themethod of claim 11, wherein the adjusting operation includes adjustingsulfur decontamination cycles of an emission control device coupled tothe engine.
 14. The method of claim 11, wherein the fuel injectorperformance includes fuel injector effects on maximum engine power. 15.The method of claim 11, wherein the amount of fuel injected can becalculated based on an exhaust air-fuel ratio and a mass airflow.